Synergistic Effect of Aminotrimethylene Phosphonic Acid (ATMP) – Al3+ System for Carbon Steel in Ground Water

The inhibition efficiency (IE) of AminoTrimethylenephosphonic acid (ATMP) in controlling corrosion of steel immersed in ground water within the absence and presence of Al3+ has been evaluated by weight loss method. It is observed that the synergistic formulation consisting of 150ppm ATMP and 50 ppm of Al3+ has 98% IE. Effect of immersion period and pH on IE has also been studied. Polarization study reveals that ATMP- Al3+ system functions as a mixed inhibitor. AC impedance study reveals that a protective film is made on the metal surface. The protective film has been analyses by FT-IR and optical microscope(SEM) studies. It is found that the protective film consists of Fe 2+ -ATMP complex. On the basis of all the above studies, a suitable mechanism of corrosion inhibition is proposed.